Plagued by stains! Giant magnetic spots on the surface of extremely hot and small stars can cause massive eruptions, study shows show
- Experts used Chile’s Very Large Telescope to study small, hot stars in the distance
- They found that these stars seemed to change in brightness periodically
- This is because bright spots on their surface come in and disappear from view
- In a few cases, the team discovered that these spots caused powerful explosions
Giant magnetic spots on the surface of extremely hot and small stars can cause massive eruptions, a study concludes.
Researchers used the Very Large Telescope in Chile to study a special kind of star in a distant cluster of stars – and found that their brightness changes.
These changes are caused by the presence of giant bright hot spots on the surface of the star that come in and out of sight as the star rotates.
The spots – caused by magnetic fields – can also give off powerful energy explosions that are considerably more powerful than anything we see on our sun.
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Giant spots on the surface of extremely hot and small stars can cause giant eruptions, a study concludes. Depicted, an artistic impression of a white spot on a horizontal branch
In their study, Yazan Momany from Padafa’s INAF Astronomical Observatory in Italy and colleagues studied a type of celestial body known as an ‘extreme horizontal branch star’ – four to five times hotter than the sun at half its mass.
“These hot and small stars are special because we know they will bypass one of the final stages of a typical star’s life and die prematurely,” said Dr. Momany.
“In our galaxy, these particularly hot objects are usually associated with the presence of a close companion.”
However, when found in the dense clusters known as ‘globular clusters’, the vast majority of these extreme horizontal branch stars are found alone.
However, when studying three different globular clusters, the researchers found that many of the extreme horizontal branch stars showed regular changes in brightness over the course of a few days to several weeks.
“After all other scenarios were eliminated, there was only one way to explain their perceived variations in brightness,” said paper author and astronomer Simone Zaggia, also of the Padua Observatory.
“These stars must be plagued with spots!” he added.
Caused by magnetic fields, spots are also seen on our own sun – although instead of being dark and relatively cool, the spots on extremely horizontal branch stars are brighter and hotter than the surrounding stellar surface.
In addition, the spots on these hot and small stars are much larger than those on our Sun – covering up to a quarter of the star’s surface – and last for decades instead of the days to months of more familiar sunspots.
It is the rotation of the stars – which shows the spots in and out of view – that cause the change in brightness that the researchers have observed in the globular clusters.
In their study, Yazan Momany from Padafa’s INAF Astronomical Observatory in Italy and colleagues studied a type of celestial body known as an ‘extreme horizontal branch star’ – four to five times hotter than the sun at half its mass. In the photo one of the four unit telescopes that make up the Very Large Telescope that the researchers used in their study
In addition to the spots, the team also found some extreme horizontal branch stars that seem to fire super flares – sudden explosions of energy.
“They look like the torches we see on our own sun, but are ten million times more energetic,” said paper author Henri Boffin of the European Southern Observatory.
“Such behavior was certainly not expected and emphasizes the importance of magnetic fields in explaining the properties of these stars.”
According to the team, the findings may help explain the origins of strong magnetic fields in many white dwarfs – the objects that represent the final stage in the life of sun-like stars, but also resemble extreme horizontal branch stars.
“Changes in the brightness of all the hot stars – from young sun-like stars to old extreme horizontal branch stars and long dead white dwarfs – could all be linked together,” said paper author David Jones of the Instituto de Astrofísica de Canarias in Spain,
“These objects can thus be perceived as collectively suffering from magnetic spots on their surfaces.”
The full findings of the study are published in the journal Natural astronomy.
WHAT IS THE VERY LARGE TELESCOPE?
The European Southern Observatory (ESO) has built the most powerful telescope ever made in the Atacama Desert in northern Chile.
It’s called the Very Large Telescope (VLT) and it is widely regarded as one of the most advanced optical instruments ever made.
It consists of four telescopes, of which The main mirrors are 27 feet (8.2 meters) in diameter.
There are also four movable auxiliary telescopes with a diameter of 1.8 meters.
The large telescopes are called Antu, Kueyen, Melipal and Yepun.
The European Southern Observatory (ESO) built the most powerful telescope ever made in the Atacama Desert in northern Chile and called it the Very Large Telescope (VLT).
The first of the Unit telescopes, “Antu”, began routine scientific operations on April 1, 1999.
The telescopes can work together to form a giant ‘interferometer’.
With this interferometer, images can be filtered for unnecessary obscuring objects and as a result, astronomers can see details up to 25 times finer than with the individual telescopes.
It has been involved in spotting the first image of an extrasolar planet and tracking individual stars moving around the supermassive black hole in the center of the Milky Way.
It also observed the afterglow of the furthest known Gamma Ray Burst,